Data from a study of device-related blood clots and the Watchman cardiac implant made by Boston Scientific (NYSE:BSX), presented today at the annual meeting of the Heart Rhythm Society in Boston, indicate the need for aggressive management of patients at risk for device-related thrombosis.

There were 74 incidences of DRT in 65 of the 1,739 Watchman patients examined in the study, or 3.7%; eight of those patients had multiple DRTs and two experienced embolic events (0.45%). There was no significant difference in mortality between patients with DRT and those without, according to the study.

Lead author Dr. Vivek Reddy, of New York’s Mt. Sinai Hospital, told MassDevice.com that the overall incidence of DRT for Watchman in the study was 3.7% using the FDA-approved strategy for anti-coagulation drugs. The surprise, Reddy told us, was the high rate of ischemic stroke in the DRT population.

“It’s surprising, not from a patho-physiological conceptual perspective, but it’s surprising because when we looked at this very early in Protect AF, again a small number of the patients in a relatively small follow-up, we did see that the subsequent stroke rate was a little bit higher, but certainly nothing like this,” he said. “We knew it was important, we knew that you had to do surveillance, we knew that if you see it you need to treat it, but we didn’t expect it to be this high.

“I think what this tells me, is that one has to be aggressive about dealing with device-related thrombus,” Reddy said, noting that it’s less clear how to proceed over the long term than in acute cases.

“It’s pretty clear how you treat it acutely – you give anticoagulation and let it dissolve,” he explained. “What’s less clear, though, is what do you do long-term after that. I think that what I would recommend, not that we have definitive data on this yet, but what I would recommend is aggressive surveillance in those patients who had device-related thrombus. I would recommend that some of them will probably require longer-term anticoagulation. That’s my guess.

“These data I don’t think take away from the argument that Watchman is a reasonable strategy. It doesn’t add or detract from the previous data. What it does do though is, I think it hones in and says when you have this you have to treat those patients aggressively,” Reddy told us.